JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<iframe id="iframe" width="640" height="360" src="https://www.youtube.com/embed/4SDVkdcO8ts" frameborder="0" allowfullscreen></iframe>
<button id="button" style="float: left">Click me!</button>

JavaScript

$(document).ready(function(){
  $("button").click(function(){
  	var ratio = $("#iframe").height() / 			 	$("#iframe").width();
    $("#iframe").width("100%");
    var newWidth = $("#iframe").width();
    $("#iframe").width(newWidth);
    $("#iframe").height(newWidth*ratio);
    $("button").text("resize the window and click me again!");
  });
});